This invention relates to a combination type stator core constituted by multilayered electromagnetic steel plates and employed in an electric rotary machine.
The Japanese Patent Application Laid-open No. 61-124241(1986) or the Japanese Utility Model Laid-open No. 5-11754(1993) discloses a combined stator core including a plurality of separate electromagnetic steel plate members combined into a multilayered structure. The Japanese Patent Application Laid-open No. 61-124241(1986) discloses an axial coupling type combined stator core including a cylindrical yoke having numerous recessed portions (i.e., groove portions) arranged at predetermined pitches in the circumferential direction and opened toward one end in the radial direction and teeth having protruding portions engaged or fitted into the recessed portions of the yoke in the axial direction.
The Japanese Utility Model Laid-open No. 5-11754(1993) discloses a radial coupling type combined stator core including a cylindrical yoke having numerous recessed portions arranged at predetermined pitches in the circumferential direction and opened toward the inner radial direction and teeth having protruding portions engaged or fitted into the recessed portions of the yoke in the radial direction.
The axial coupling type combined stator core disclosed in the above-described Japanese Patent Application Laid-open No. 61-124241(1986) is easy to manufacture and is advantageous in preventing the teeth from being pulled out in the radial directions. However, as the yoke and teeth are constituted by electromagnetic steel plates being multilayered, the surfaces of the recessed portions and the protruding portions formed on the yoke and teeth remain uneven or undulated. If required to reduce the gap formed between the recessed portions and the protruding portions when the yoke and teeth are engaged or fitted, constituting the yoke and teeth with the electromagnetic steel plates being multilayered will become difficult.
On the other hand, the above-described radial coupling type combined stator core disclosed in the Japanese Utility Model Laid-open No. 5-11754(1993) can solve the problem of the above-described axial coupling type combined stator core. However, the radial coupling type combined stator core is inferior to the axial coupling type combined stator core in that the circumferential width of each recessed portion cannot be reduced so much at its opening end. Thus, there is a problem that the teeth may be pulled out the yoke in the radial direction due to magnetic vibrations. Not only the combined stator cores disclosed in the Japanese Patent Application Laid-open No. 61-124241(1986) and the Japanese Utility Model Laid-open No. 5-11754(1993) but also many of other conventional combined stator cores have a problem in that it is difficult to eliminate the gap (or clearance) between the teeth and yoke formed when they are faced with each other. Accordingly, when electric power is supplied to a stator coil, the magnetic vibrations caused by the stator core induce chattering vibrations in the teeth and accordingly generate noises. Furthermore, the magnetic resistance in the above-described gap is so large that the efficiency of the electric rotary machine decreases significantly.